Systemic Helicobacter infection and associated mortalities in endangered Grand Cayman blue iguanas (Cyclura lewisi) and introduced green iguanas (Iguana iguana)

Abstract

The Blue Iguana Recovery Programme maintains a captive breeding and head-starting program for endangered Grand Cayman blue iguanas (Cyclura lewisi) on Grand Cayman, Cayman Islands. In May 2015, program staff encountered two lethargic wild Grand Cayman blue iguanas within the Queen Elizabeth II Botanic Park (QEIIBP). Spiral-shaped bacteria were identified on peripheral blood smears from both animals, which molecular diagnostics identified as a novel Helicobacter species (provisionary name Helicobacter sp. GCBI1). Between March 2015 and February 2017, 11 Grand Cayman blue iguanas were identified with the infection. Two of these were found dead and nine were treated; five of the nine treated animals survived the initial infection. Phylogenetic analysis of the 16S rRNA gene suggests Helicobacter sp. GCBI1 is most closely related to Helicobacter spp. in chelonians. We developed a Taqman qPCR assay specific for Helicobacter sp. GCBI1 to screen tissue and/or blood samples from clinical cases, fecal and cloacal samples from clinically healthy Grand Cayman blue iguanas, including previously infected and recovered iguanas, and iguanas housed adjacent to clinical cases. Fecal and/or cloacal swab samples were all negative, suggesting that Grand Cayman blue iguanas do not asymptomatically carry this organism nor shed this pathogen per cloaca post infection. Retrospective analysis of a 2014 mortality event affecting green iguanas (Iguana iguana) from a separate Grand Cayman location identified Helicobacter sp. GCBI1 in two of three cases. The source of infection and mode of transmission are yet to be confirmed. Analysis of rainfall data reveal that all infections occurred during a multi-year dry period, and most occurred shortly after the first rains at the end of seasonal drought. Additionally, further screening has identified Helicobacter sp. GCBI1 from choanal swabs of clinically normal green iguanas in the QEIIBP, suggesting they could be asymptomatic carriers and a potential source of the pathogen.

Helicobacter cyclurae sp. Nov., Isolated From Endangered Blue Iguanas (Cyclura lewisi)

“…Also, our culture and PCR results indicated that H. cyclurae was more commonly identified in the feces and cloacal samples from clinical normal animals in our study compared with Helicobacter sp. GCBI1 identified in clinically ill iguanas in blood and tissue samples (Conley et al, 2021). In our previous study, clinically ill blue iguanas who developed lethargy, weakness, inappetence, and septicemia had spiral-shaped bacteria identified on peripheral blood smears (Conley et al, 2021).…”

“…GCBI1 identified in clinically ill iguanas in blood and tissue samples (Conley et al, 2021). In our previous study, clinically ill blue iguanas who developed lethargy, weakness, inappetence, and septicemia had spiral-shaped bacteria identified on peripheral blood smears (Conley et al, 2021). Through 16S rRNA genespecific primers, Helicobacter spp.…”

“…GCBI1 was the causative agent of disease in Grand Cayman blue iguanas. Retrospective analysis from a mortality event of green iguanas a year prior and screening of healthy free-ranging green iguanas from QEIIBP also found this helicobacter by qPCR (Conley et al, 2021). In this paper, we describe, by utilizing molecular and microbiological methodology, the isolation of a novel Helicobacter species, H. cyclurae, that is distinct from previously described Helicobacter sp.…”

“…The 16S rRNA sequences of this novel Helicobacter species were different from the Helicobacter sp. GCBI1, which was identified by PCR in the blood and tissues of blue iguanas; these two Helicobacters only shared 96% sequence identity (Figure 1A; Conley et al, 2021). The housekeeping gene sequences for heat shock protein 60 (hsp60) and DNA gyrase subunit B (gyrB) have been used for classification of phylogenetic relationships among Helicobacter species (Mikkonen et al, 2004;Hannula and Hanninen, 2007).…”

“…Reptiles are also colonized by Helicobacter spp., with one report finding a prevalence of 4.8 and 39.1% by culture and PCR, respectively, and more specifically 7.4 and 30.7% for animals of the suborder Lacertilia (Gilbert et al, 2014). In a recent study, two free-ranging blue iguanas located at the Grand Cayman Queen Elizabeth II Botanic Park (QEIIBP) in 2015 developed hind limb paralysis and septicemia with spiral-shaped bacteria noted on blood smears (Conley et al, 2021). PCR results, using specific Helicobacter species primers, from the blood and tissue of these animals were positive for a novel Helicobacter species, provisionally designated Helicobacter sp.…”